Process for forming twisted fibre assemblies



PRocEss FOR FoRMING TWISTED FIBRE AssEMBLIEs D..E. HENSHAW ETAL 2' Sheets-Sheet l Feb. 28, 1967 Filed Feb.

Fel 28, 1957 D. E. HENsHAw ETAI. 3,306,023

PROCESS FOR FORMING TWISTED FIBRE ASSEMBLIES `Filed Feb. 9, 1966 2 Sheets-Sheet 2 United States Patent Otlce 3,306,023 Patented Feb. 28, 1967 orate p Filed Feb. 9, 1966, Ser. No. 526,128 Claims priority, application Australia, Feb. 9, 1965, 54,921/65 5 Claims. (Cl. 57-156) This invention relates to the formation of twisted fibre assemblies and is applicable particularly but not exclusivel1y to the preparation of yarn from staple iibres, for example wool libres.

The specification of our United States Patent No. 2,225,533. discloses the preparation of a yarn by converging a strand which has been twisted so that it has repeated along its length alternating zones of opposite twist with another strand and allowing it to twist around that other strand. Both of the strands, or all of them if there be more than two, may be intermittently twisted and converged with the regions of twist in the strands suitably phased so that, when the strands commence to untwist, they twist around each other and this plying of the strands restrains the twist in each individual strand to result in self-stabilized plied assembly. Such an assembly will hereinafter, for the sake of convenience, be called selftwistthread or, where appropriate, more specifically, a self-twist yarn and the individual components will be called strands A self-twist yarn can be produced at much faster rates than conventional plied yarns. However, simple selftwist yarns have regions of no plying twist which have low abrasion resistance and also constitute zones of weakness in the yarn. The weaving of simple self-twist yarns therefore can lead to yarn breakage problems in the warp. Furthermore the regions of no twist may cause a periodicity effect in the appearance of a fabric woven from -a simple self-twist yarn, particularly if the fabric is woven in a single colour. The appearance of such a fabric may render it unsuitable for some applications.

A weavable self-twist warp yarn can be produced by suitably phasing the twist change-over regions of the individual strands of the yarn as fully described in our above mentioned co-pending applications, but su-ch yarns may still produce fabrics which suier from a periodicity in appearance.

A weavable yarn of satisfactory appearance can be obtained 'by plying together two or more self-twist yarns. However, because of the increased number of strands in a yarn of given size, each individual strand must be relatively iine and this leads to breakage problems when the individual strands are being separately twisted.

It is an object of this invention to provide a process for the production of yarn which can be readily Woven. It is a further object to provide such a -process where-by there may be produced, if desired, a yarn which can be used to produce a single colour fabric of relatively even appearance.

According to the invention there is provided a process for forming a twisted thread fromtwo strands, compri-sing separately twisting the strands so that they each have repeated along their lengths alternating zones of opposite twist separated by twist change-over regions at which there is no twist, converging the strands so that they twist around one another to form a stable thread, and then inserting unidirectional twist into that thread.

Contrary to what might be excepted, the strongest yarn is obtained by applying unidirectional twist not to a selftwist yarn which has -been phased so :as to give maximum strength, but instead to the weaker form of self-twist yarn, i.e. a self-twist yarn in which the twist change-over regions of the individual strands are coincident and the twist zones of the individual strands are completely in phase.

The unidirectional twist may be inserted until the thread has unidirectional plying twist which, however, varies in intensity along the length of the thread.

In order that the invention may be more fully explained; the preparation of a two strand thread by a process according to the invention will now be descri'bed with reference to the accompanying drawings in which:

FIGURE 1 is a diagrammatic representation of a selftwist yarn formed of two intermittently twisted strands with their twist zones of equal length and in phase,

FIGURE 2 is a diagrammatic representation of the configuration taken on by the yarn of FIGURE 1 after a certain amount of unidirectional S-twist has been inserted -into it,

FIGURE 3 is a diagrammatic representation of the configuration taken on by the yarn when even further S- twist is inserted into it, and

FIGURE 4 is a graphic illustration of the manner in which the strength of fa self-twist yarn is increased by the insertion of unidirectional twist into it.

FIGURE 1 illustrates diagrammatically a self-twist yarn consisting of two similar alternately opposite-ly twisted strands 5, 6 which -are plied with their twist zones in phase. This type of yarn may be produced by apparatus of a type which is fully described and illustrated in the specification of the above mentioned United States patent and the yarn is identical to the one illustrated in FIGURE lla of that specification. It is lformed by separately twisting strands 5, 6 so that they each haverepeated along their length alternating zones of opposite twist separated .by twist change-over regions at which there is no twist and then converging strands 5, 6 with like twist zones in phase and with the twist change-over regions coincident. Strands 5, 6 then twist around one another to form the stable yarn shown in the ligure. The yarn has alternating zones A and B of opposite plying twist separated by `short zones C of no plying twist. Throughout zones C there is no twist in either of strands 5, 6, these zones being formed by coinciding twist change-over regions of the strands. Throughout zones A, the individual strands 5, 6 .have Z-twist and the yarn has two-fold or plying S- twist. Throughout zones B, the individual strands 5, 6 have S-twist and the yarn has two-fold Z-twist.

In accordance with this invention unidirectional twist maybe inserted into the yarn of FIGURE 1 until its plying twist is all in the direction of the linserted unidirectional twist. For example, consider that S-twist is added to the yarn. Over zones A in which the individual strands 5, 6 have Z-twist and the yam has two-fold S-twist, the twofold S-twist is reinforced; two-fold S-twist is imparted to the yarn over zones C which originally had no twist; and in zones B, where the individual strands 5, 6 have S- twist and the yarn has two-fold Z-twist, the two-fold twist is removed. A stage is reached at which zones B have no two-fold or plying twist at all. The configuration of the yarn at this stage is shown in FIGURE 2. The twofold S-twist of the yarn over zones A has been reinforced, two-fold S-twist has been inserted into the yarn over zones C and the two-fold Z-twist has been removed from the yarn over zone B so that zones B are now large zones which have no two-fold twist at all. However, strands 5, 6 still have individual S-twist throughout zones B.

If the insertion of the two-fold S-twist is now continued the two-fold S-twist in zones A and C is further reinforced and throughout zones B the strands 5, 6 are plied with two-fold S-twist. The Iinal yarn is shown in FIG- URE 3. It has alternating zones A and B of relatively high intensity two-fold S-twist and relatively low intensity two-fold S-twist which are separated by short zones C of medium intensity two-fold S-twist. Zones C are the ones which in the original stable self-twist yarn had no twist at all and constituted weak zones in that y-arn. Because they have now been strengthened by the insertion of twist therein, the strength of the yarn as a whole is greatly increased. In fact the strength of the yarn increases as soon as the insertion of unidirectional twist is begun. Although in the initial stages of the insertion of the unidirectional twist, zones B are weakened by the removal of two-fold twist, the strands in these Zones have individual twist and the yarn in these zones is therefore stronger than the yarn over Zones C.

The increase of strength of the yarn as unidirectional twist is inserted into it is shown graphically in FIGURE 4, in which the yarn strength is shown on axis OY against the inserted unidirection twist on `the axis OX. In this figure, the line L shows a typical result. However the actual rate of increase of strength will depend on several factors such as the intensity of the twist in the original self-twist yarn and the number of strands in the yarn. For example, a self-tvvist yarn similar to that resulting in curve L but having a greater intensity of self-twist would give the result represented by curve M whereas a selftwist yarn having a smaller intensity of self-twist would give the result shown by curve N. In all cases, however, the strength of the yarn is greatly increased by the insertion of the unidirectional twist.

It has been found that single colour fabrics woven from simple self-twist yarn may show, under unfavourable lighting conditions, visible patterning effects which are unsightly. The reason for this is not fully understood 'but it is thought that the reilective properties of a yarn surface may vary according to whether or not the yarn has two-fold S-twist or two-fold Z-twist. In the case of yarn having unidirectional twist of varying intensity, this objectionable patterning does not occur, or at least does not occur to an extent sufcient to be visible to the naked eye. A fabric woven from a yarn of this type therefore has an even appearance.

It will be appreciated that similar results could be achieved by applying unidirectional two-fold Z-twist to the self-twist yarn rather than S-twist. Furthermoreby stopping the insertion of the unidirectional twist into the yarn at such -a stage that the yarn has alternating Zones of oppositely directed two-fold twist or when alternate zones have no twist at all, it is possible to produce special effects in the resultant fabric. Moreover the self-twist yarn need not be a two strand yarn but could comprise three or more strands. It is, therefore, to be understood that -the invention is in no way limited to the production of a two strand yarn 4as described in detail above 'but includes all modications and adaptations which fall within its spirit and scope.

We claim:

1. A process for forming a twisted thread from at least two strands, comprising the steps of:

(a) separately twisting the strands so that they each have repeated along their lengths alternating Zones of opposite twist separated by twist change-over regions at which there is no twist,

(b) converging the strands so that they twist around one another to form a stable thread, and

(c) inserting unidirectional twist into said sta'ble thread.

2. A process as claimed in claim 1, wherein the strands are converged with like twist zones in phase :and with the twist change-over regions coincident when forming said stable thread.

3. A process `as claimed in claim 1, in which said unidirectional twist is inserted into the stable thread until that thread has unidirectional plying twist which varies in intensity along the length ofthe thread.

4. A process as claimed in claim 2, in which said unidirectional twist is inserted into the stable thread until that thread has unidirectional plying twist which varies in intensity along the length of the thread.

5. A process as claimed in claim 1, in which at least one of the strands is produced from staple fibre.

References Cited by the Examiner UNITED STATES PATENTS 2,203,721 6/1940 Dngley et al. 57-157 2,807,130 9/1957 Trapido et al. 57-77.3 2,936,569 5/1960 Mull 57-140 2,957,302 10/1960 Lenk et al. 5777.3 2,990,671 7/1961V Bunting et al 57-77.3 X 3,041,814 7/ 1962 Held 57--34 3,162,995 12/1964 Corner et al 57-157 3,225,533 12/1965 Henshaw 57-156 X References Cited by the Applicant UNITED STATES PATENTS 3,120,733 2/1964 Breen.

FRANK J. COHEN, Primary Examiner.

D. E. WATKINS, Assistant Examiner. 

1. A PROCESS FOR FORMING A TWISTED THREAD FROM AT LEAST TWO STRANDS, COMPRISING THE STEPS OF: (A) SEPARATELY TWISTING THE STRANDS SO THAT THEY EACH HAVE REPEATED ALONG THEIR LENGTHS ALTERNATING ZONES OF OPPOSITE TWIST SEPARATED BY TWIST CHANGE-OVER REGIONS AT WHICH THERE IS NO TWIST, (B) CONVERGING THE STRANDS SO THAT THEY TWIST AROUND ONE ANOTHER TO FORM A STABLE THREAD, AND (C) INSERTING UNIDIRECTIONAL TWIST INTO SAID STABLE THREAD. 